1. Field of the Invention
The present invention relates to a method and apparatus for controlling the temper-rolled profile of a cold rolled steel strip after continuous annealing.
In recent years, more and more of cold rolled steel sheets and strips are produced through a continuous production line in which a continuous annealing furnace, a temper-rolling mill and a refining section. It is a general requirement for cold rolled steel sheets and strips that they should have a good profile with excellent flatness in particular, but in event a cold rolled steel strip produced through the continuous production line should have an unsatisfactory profile, it is very difficult to perform a re-rolling for correcting the unsatisfactory profile. Therefore, for production of steel sheets which are required to meet with a severe requirement of flatness, high-tension steel sheets and steel sheets which are required to be subjected to a large reduction by temper-rolling (hereinafter called "high temper reduction materials" normally they are subjected to 5% or higher reduction by temper-rolling), a four-high temper-rolling mill followed by a leveller for correcting the profile is conventionally provided after the continuous annealing furnace in the continuous production line.
Therefore, the conventional art has problems that the whole length of the continuous production line must be considerably increased and the capital cost is inevitably increased, and that a steel sheet which is levelled by a tension leveller in addition to the temper-rolling has defects that the ageing phenomenon appears prematurely and deterioration of the mechanical properties due to the ageing is remarkable and thus the workability of the resultant cold rolled strip or sheet is poor.
Moreover, various grades and sizes of steel sheets and strips are produced by the continuous production line.
For increasing the production rate, strips of different sizes and compositions are welded together between the finishing end of a preceding strip and the starting end of a subsequent strip (welded point), so that they are continuously passed through the rolling mill.
Therefore, when the temper-rolling is performed by a four-high temper-rolling mill, such disadvantages are induced that the rolls must be replaced more frequently and a more number of rolls must be preserved for the replacement, because the rolls must be replaced with ones having a proper roll curve in accordance with the sizes, compositions, rolling reduction rates of the steel sheets and strips to be rolled.
Further, when a four-high temper-rolling mill is used for the temper-rolling, there is brought about such problems that the rolled profile of steel sheets and strips is severely destroyed if the change in the sheet width is large at the time of passage of the welding point, and rolling problems such as wrinkling are easily caused so that the strip walk in the width direction is considerably limited at the time of the size-change operation, thus hindering a proper adjustment of the pass schedule.
2. Summary of the Invention
Therefore, one of the objects of the present invention is to provide a method and apparatus for temper-rolling suitable for use in the continuous production line, without the disadvantages and defects as hereinbefore mentioned.
The aforementioned object of the present invention is achieved by performing the temper-rolling simultaneously with the profile controlling with use of a six-high rolling mill stand of intermediate roll shifting type.
The present invention may be summarized as below:
(1) A method for controlling a temper-rolled profile of a cold rolled steel strip after continuous annealing, comprising subjecting the continuously annealed cold rolled steel strip simultaneously to temper-rolling and profile controlling by use of a six-high rolling mill of intermediate roll shifting type in the same production line. PA1 (2) A continuous annealing apparatus comprising: a continuous annealing furnace, a temper-rolling section and a refining section, said temper-rolling section being provided with a six-high temper-rolling mill of intermediate roll shifting type, composed of the upper three rolls and the lower three rolls, and the intermediate rolls in the upper and lower three rolls are designed to be shiftable in the axial direction, and being omitted of a profile controlling device.